yum命令用ctrl+z命令中断后，再运行yum时，出现：
Existing lock /var/run/yum.pid: another copy is running as pid 3046. Another app is currently holding the yum lock; waiting for it to exit... Another app is currently holding the yum lock; waiting for it to exit... Another app is currently holding the yum lock; waiting for it to exit... Another app is currently holding the yum lock; waiting for it to exit... Another app is currently holding the yum lock; waiting for it to exit...
解决方案：
rm -f /var/run/yum.pid /sbin/service yum-updatesd restart Stopping yum-updatesd: [ OK ] Starting yum-updatesd: [ OK ]
yum-updatesd上系统自带的一个提供系统更新的服务，安装文件也叫做yum-updatesd，这个服务默认是自动启动的（init 5），因为系统只允许一个更新进程在运行，所以他运行的时候会自动给yum加锁，这就导致了开机后不能手动进行yum了。